One-piece anti-drainback and relief valve

ABSTRACT

A spin-on fluid filter of the type having a hollow, cylindrical filter element enclosed within an outer container and an end plate, is provided with a one-piece, combination anti-drainback and relief valve. The valve includes an axially movable cylindrical sleeve, one end thereof being disposed within the filter element, and the other end thereof normally engaging the end plate radially inwardly of the inlet ports and radially outwardly of the outlet port formed in the end plate. A resilient annular seal extends from the sleeve to normally engage the end plate radially outwardly of the inlet ports. A spring is disposed within the filter element for normally urging the cylindrical sleeve downwardly into engagement with the end plate. The diameters of the end portions of the spring are preferably smaller than the diameter of the central portion thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluid filter and, more particularly,to a one-piece, combination anti-drainback and relief valve for adisposable, spin-on oil filter.

2. Summary of Related Art

Spin-on oil filters are well known devices often used in the oilcirculation system of internal combustion engines to filter out smallparticulate matter which would otherwise abrade moving engine parts.These filters generally include a cylindrical outer container and an endplate enclosing a hollow, cylindrical filter element. Plural inlet portsand a central outlet port are provided in the end plate to allow oil tocirculate through the filter element. The central outlet port istypically threaded for "spin-on" mounting of the filter to an enginefilter mount. An annular gasket is utilized for effecting a seal betweenthe filter and the engine mount or adapter plate on which the filter ismounted.

Such filters are also generally provided with an anti-drainback valveand pressure relief valve. The anti-drainback valve prevents the gravityinduced, drainage of oil from the filter which would otherwise occurwhen the engine is not operating. This feature is desirable since adrained oil filter results in a momentary interruption in thecirculation of oil when the engine resumes operation. A pressure reliefvalve is also generally utilized in this type of filter to permit oilflowing through the filter to bypass the filter element when apredetermined pressure threshold is surpassed due to the build-up ofcontaminants in the filter element.

In practice, the anti-drainback valve and pressure relief valve havegenerally consisted of separate elements, adding substantially to themanufacturing cost of the filter. Overall, it is clearly desirable thatthe manufacturing cost of the valve assemblies for such filters beminimized, since these filters are generally disposable.

Combined anti-drainback and relief valves have been proposed, but havegenerally required a plurality of elements associated with the valve toachieve the desired operation. The complexity of such valves addssignificantly to the cost of both the materials and the assemblythereof, making such filters relatively expensive. A cost-effectiveone-piece, combination anti-drainback and relief valve which provideseffective valve operation and long-term sealing properties has beenheretofore unavailable.

In addition, such conventional spin-on oil filters typically include aperforated metal center tube disposed axially within a pleated paperfilter element. The perforated center tube laterally supports the filterelement, while allowing oil to pass from the filter element down throughthe center tube and out of the filter unit. In order to maintain asufficient collapse strength, the size and number of perforations islimited, so that the center tube may in practice unduly impede the flowof oil therethrough. Additionally, a spring is generally requiredbetween the end of the filter element and the closed end of thecontainer, to hold the filter element in position.

In view of the foregoing, replacement of the perforated metal centertube with a helical compression spring has been proposed. The use of aspring disposed axially within the filter element is advantageous inthat there is a significantly greater open area for oil to flow throughwhen compared with the conventional perforated center tube, while aneven greater collapse strength is provided. However, the ends of suchsprings are typically sharp, and often damage the inner surface of thepaper filter element.

SUMMARY OF THE INVENTION

The present invention relates to a fluid filter comprising an outercontainer having a closed end and an open end, and an end plate securedwithin the open end of the container. The end plate is provided with acentral fluid outlet port and plural fluid inlet ports disposed aroundthe outlet port. A hollow, cylindrical filter element is enclosed withinthe container behind the end plate. A combination anti-drainback andrelief valve is provided which includes an axially movable cylindricalsleeve, the upper end thereof being disposed within the filter element.The lower end of the sleeve normally engages the end plate radiallyinwardly of the inlet ports and radially outwardly of the outlet port. Aresilient annular lip extends from the sleeve to normally engage the endplate radially outwardly of the inlet ports. Biasing means are disposedwithin the filter element for normally urging the cylindrical sleevedownwardly into engagement with the end plate.

The force exerted by the biasing means is overcome at a predeterminedpressure, at which point the sleeve is moved axially away from the endplate to allow fluid to by-pass the filter element. In addition, theresilient annular seal of the valve operates as an anti-drainback valveto prevent the reverse flow of oil through the filter and out the inletports. The novel construction of the present invention thus provides aone-piece, combination anti-drainback and relief valve for a fluidfilter.

In a preferred embodiment of the invention, the biasing means comprisesa barrel-shaped helical spring disposed within the filter element andhaving smaller diameter end portions and a larger diameter centralportion. The barrel shape of the spring is advantageous in that both ofthe free ends of the spring, which are typically sharp, are positionedradially inwardly of the inner surface of the filter element,eliminating any of the tearing or other damage the ends might otherwisecause to the pleated paper filter element. Thus, this aspect of theinvention may also be advantageously incorporated into filter unitsprovided with conventional anti-drainback valves and separate pressurerelief valves, replacing the conventional perforated metal center tubecurrently used therewith.

BRIEF DESCRIPTION OF THE DRAWING

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description of a preferred embodiment when considered in thelight of the accompanying drawings in which:

FIG. 1 is a side elevational view, partially in longitudinal section, ofa filter unit including a one-piece anti-drainback and relief valve inaccordance with the present invention;

FIG. 2 is a sectional view of a portion of the filter unit illustratedin FIG. 1, showing the combination valve operating as a relief valve;

FIG. 3 is a side elevational view, partially in longitudinal section, ofa filter unit having a spring center tube in accordance with an aspectof the present invention, and provided with a conventionalanti-drainback valve and separate relief valve;

FIG. 4 is a sectional view of an alternate embodiment of a filter unitprovided with a one-piece anti-drainback and relief valve in accordancewith the present invention;

FIG. 5 is a sectional view of an additional embodiment of a filter unitprovided with a one-piece anti-drainback and relief valve in accordancewith the present invention;

FIG. 6 is a top end view of the valve shown in FIG. 5;

FIG. 7 is a side elevational view, partially in longitudinal section, ofanother embodiment of a filter unit including a one-piece anti-drainbackand relief valve in accordance with the present invention; and

FIG. 8 is a sectional view of an additional embodiment of the one-pieceanti-drainback and relief valve of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, there is illustrated in FIGS. 1 and 2 adisposable, spin-on filter unit in accordance with the present inventiongenerally designated by the numeral 10. The filter unit 10 includes anouter housing or container 12 which is closed at one end by an integralend wall 14. The other end of the container 12 is provided with areinforcing end plate 16 and an annular end cover 18. A gasket 20 formedof an oil resistant elastomeric material, such as nitrile rubber or thelike, is disposed within an annular seating recess 22 formed on thelower side of the end cover 18. The gasket 20 is adapted to provide afluid-tight seal for an oil inlet chamber (not shown) that is formedwhen the filter unit 10 is operatively mounted on a filter mount of, forexample, an internal combustion engine.

The end plate 16 is provided with a centrally located outlet port 24formed by an internally threaded neck 25 adapted to be screwed onto anexternally threaded post or standpipe (not shown) having a centralpassage for the flow of oil from the filter unit 10 back to the engine.The end plate 16 is also provided with a plurality of inlet ports 26which allow the oil to be filtered to flow into the interior of thefilter unit 10. A hollow, cylindrical filter element 28 formed ofconventional resin impregnated pleated paper or other suitable filtermaterial is disposed within the outer container 12. A circular end cap30 is secured to the end of the filter element 28 adjacent the closedend wall 14 of the container 12 to seal off the upper end of the filter.An annular seal 32, formed of a urethane polymer or other suitablematerial, is secured to the opposite end of the filter element 28. Theannular seal 32 is preferably integrally molded to the end of the filterelement 28.

A one-piece, combination anti-drainback and relief valve generallyindicated by the numeral 34 is disposed between the filter element 28and the end plate 16, surrounding the outlet port 24. The valve 34 moreparticularly comprises a rigid, cylindrical sleeve 36 mounted within thefilter element 28 and annular seal 32, and adapted for sliding axialmovement relative thereto. The sleeve 36 is of a sufficient length sothat the outer periphery thereof maintains a sealing engagement with theannular seal 32 throughout the range of axial sliding movement of thesleeve 36, thereby preventing oil from by-passing the filter element 28by flowing between the upper end of the sleeve 36 and the filter element28. The sleeve 36 may be formed of any sufficiently strong, rigid andoil resistent material, and is preferably formed of a moldable polymericmaterial. It has been found that nylon is one such suitable material.

The lower end of the sleeve 36 terminates in a tubular extension 38having an outer diameter which is less than the outer diameter of theupper portion of the sleeve 36. The extension 38 is preferably providedwith a plurality of circumferentially spaced, radially inwardlyprojecting tabs 39 which loosely engage the neck 25. The tabs 39 therebyfacilitate the orientation of the valve 34 relative to the end plate 16during assembly of the filter unit 10. A helical compression spring 40disposed coaxially within the filter element 28 engages the centralportion of the end cap 30 and the upper end of the sleeve 36, andnormally urges the sleeve 36 downwardly into sealing engagement with theend plate 16 at a position radially inwardly of the inlet ports 26.

The lower end of the of the sleeve 36 also carries an annular, resilientlip 42 formed of a suitable flexible material, such as nitrile rubber,silicone or the like. The lip 42 extends downwardly and radiallyoutwardly from the sleeve 36 to engage the end plate 16 radiallyoutwardly of the inlet ports 26. The lip 42 thus forms a seal with theend plate 16 and prevents flow out of the filter through the inlet ports26 when the engine is not operating. The resilient lip 42 will disengagefrom the end plate 16 upon the application of a relatively low pressurecreated by oil flow through the inlet ports 26 as shown in FIG. 1, andwill close when no such pressure is applied. The combination valve 34may be formed as a one-piece unit by permanently mounting the lip seal42 to the sleeve 36 with an adhesive, providing a stretch fit, or othersuitable means of attachment. Preferably, the entire valve 34 is moldedto form a one-piece unit.

During normal operation, oil which enters the filter unit 10 through theinlet ports 26 flows upward and radially outwardly, forcing the distalend of the resilient lip 42 away from the end plate 26 to provide apassage therebetween. The oil flows axially about and through the filterelement 28 into a center tube, preferably formed by the spring 40,disposed co-axially within the filter element 28. The spring 40 in thatcase extends the entire length of the filter element 28 to engage thecenter portion of the end cap 30. The center tube may also be formed ofa conventional perforated metal tube, as discussed in more detail belowwith reference to FIG. 7. Oil within the spring 40 exits the filter unit10 through the outlet port 24, flowing back through the central passagein the standpipe to the engine.

As long as the filter element 28 is not unduly clogged, the tubularextension 38 of the cylindrical sleeve 36 will remain in sealingengagement with the end plate 16 due to the force of the spring 40.Should the filter element 28 become sufficiently clogged withcontaminants so as to cause a build up of pressure at the inlet ports 26above a predetermined amount, the force applied to the sleeve 36 by thespring 40 will be overcome, and the sleeve 36 will be moved upwardlyfrom the position shown in FIG. 1 to the position shown in FIG. 2. Theextension 38 is thereby disengaged from the end plate 16 to allow theflow of oil around the edge of the extension 38, around and between thetabs 39, and exiting through the outlet port 24. The oil is therebyallowed to by-pass the clogged filter element 28 to supply the necessaryoil to the engine parts despite the clogging of the filter element 28.Should the filter element 28 become clogged to an even greater extent,the pressure developed at the inlet ports 26 will be increased, furtheroffsetting the load of the spring 40 to move the end of the extension 38farther away from the end plate 16. This allows a greater flow of oil toby-pass the filter element 28 in response to an increase in the cloggedcondition of the filter element 28. Likewise, should there be areduction in the restriction of the filter element 28 and the pressurecaused thereby, the spring 40 will urge the sleeve 36 and extension 38closer to the end plate 16, reducing the flow of oil by-passing thefilter element 28.

The spring 40 is preferably generally barrel shaped, having smallerdiameter end portions 41 and 43 and a larger diameter central portion45. The central portion 45 of the spring 40 exerts forces radiallyoutwardly against the inner surface of the filter element 28 tostabilize and prevent the collapse of the filter element 28 from thehigh oil pressure developed at the outer periphery of the filter element28. As noted above, the spring 40 also exerts forces axially between theend wall 13 of the container 12 and the sleeve 36 of the combinationanti-drainback and relief valve 34. Forming the spring 40 with the endportion 41 having a diameter less than the diameter of the centralportion 45 facilitates the engagement of this end portion 41 against theupper end of the sleeve 36. The spring 40 is also preferably providedwith ground ends, both end portions 41 and 43 being substantially flatto further enhance the engagement between the end portions 41 and 43 andthe sleeve 36 and end cap 30, respectively.

The barrel shape of the spring 40 is also advantageous in that both ofthe free ends of the spring, which are typically sharp, are positionedradially inwardly of the inner surface of the filter element 28,eliminating any of the tearing or other damage the ends might otherwisecause to the pleated paper filter element 28. The barrel shaped springcenter tube 40 may thus be advantageously used with filter unitsprovided with conventional anti-drainback valves and separate pressurerelief valves, replacing the conventional perforated metal center tubecurrently used therewith. This aspect of the present invention is shownin FIG. 3.

In FIG. 3, the filter unit 50 includes an outer container 52 which isclosed at one end by an integral end wall 54. The other end of thecontainer 52 is provided with a reinforcing end plate 56. The end plate56 is provided with a centrally located outlet port 58 formed by aninternally threaded neck 60 adapted to be screwed onto an externallythreaded post or standpipe (not shown). The end plate 56 is alsoprovided with a plurality of inlet ports 62 which allow the oil to befiltered to flow into the interior of the filter unit 50. A hollow,cylindrical filter element 64 formed of conventional resin impregnatedpleated paper or other suitable filter material is disposed within theouter container 52. A circular end cap 66 is secured to the end of thefilter element 64 adjacent the closed end wall 54.

A barrel shaped helical compression spring 68 is disposed within thefilter element 64 of the filter unit 50. The spring 68 has smallerdiameter end portions 70 and 72 and a larger diameter central portion73. The upper end 70 of the spring 68 engages the circular end cap 66,which in turn abuts the end wall 54 of the outer container 52. The lowerend 72 of the spring 68 engages the upper end 74 of a housing 76enclosing a conventional pressure relief valve 78. The filter unit 50 isalso provided with a conventional separate anti-drainback valve 80disposed adjacent the end plate 56. By positioning the ends 70 and 72 ofthe spring 68 radially inwardly of the inner surface of the filterelement 64, any tearing or other damage the ends might otherwise causeto the pleated paper filter element 64 is avoided. Additionally, thebarrel shape of the spring 68 facilitates the insertion of the spring 68within the filter element 64 during assembly of the filter unit 50.

In an alternate embodiment of the combination anti-drainback and reliefvalve of the present invention, illustrated in FIG. 4, a cylindricalsealing element, preferably formed as an L-shaped sleeve 90, is securedto the lower end of the filter element 28 by any suitable means, such asby an adhesive. The L-shaped sleeve 90 may be formed of any sufficientlystrong, rigid material having a relatively smooth surface, and ispreferably formed of steel. The one-piece, combination anti-drainbackand relief valve 92 comprises a rigid, cylindrical sleeve 94 mountedwithin the filter element 28 and L-shaped sleeve 90, and adapted forsliding axial movement relative thereto. As in the first embodiment ofthe combination valve, the lower end of the sleeve 94 terminates in atubular extension 96 which is preferably provided with a plurality ofcircumferentially spaced, radially inwardly projecting tabs 98. Thelower end of the sleeve 94 also carries a resilient lip 100 extendingdownwardly and radially outwardly from the sleeve 94 to engage the endplate 16 radially outwardly of the inlet ports 26. The lip 100 thusforms a seal with the end plate 16 and prevents flow out of the filterthrough the inlet ports 26 when the engine is not operating.

The outer surface of the sleeve 94 is provided with an annular seal 102which sealingly engages the axially extending portion 104 of theL-shaped sleeve 90. The L-shaped sleeve 90 is of sufficient length, andthe seal 102 is so positioned, that a sealing engagement is maintainedtherebetween throughout the range of axial sliding movement of thesleeve 94. The combination valve 92 may be formed as a one-piece unit bypermanently mounting the lip seal 100 and the seal 102 to the sleeve 94with an adhesive or other suitable means of attachment. Preferably, theentire valve 92 is molded to form a one-piece unit.

The seal 102 may be comprised of any suitable elastomeric material, suchas a urethane polymer or nitrile rubber, for example. The seal 102 mayalso be of any suitable construction, such as the multiple lip wipertype seal illustrated in FIG. 4, the O-ring illustrated in FIG. 5 anddiscussed below, or another suitable seal, such as a series of O-rings,for example.

The valve 92 operates in much the same way as the valve 34 illustratedin FIGS. 1 and 2 and discussed above. The resilient lip 100 willdisengage from the end plate 16 upon the application of a relatively lowpressure created by oil flow through the inlet ports 26, and will closewhen no such pressure is applied. Should the filter element 28 becomesufficiently clogged so as to cause a build up of pressure at the inletports 26 above a predetermined amount, the force applied to the sleeve94 by the spring 40 will be overcome, and the sleeve 94 will be movedupwardly. The tubular extension 96 is thereby disengaged from the endplate 16 to allow the flow of oil around the edge of tubular extension96, around and between the tabs 98, and exiting through the outlet port24, thereby allowing the oil to by-pass the clogged filter element 28.Should there be a reduction in the restriction of the filter element 28and the pressure caused thereby, the spring 40 will urge the sleeve 94and tubular extension 96 closer to the end plate 16. During any axialmovement of the sleeve 94, the annular seal 102 maintains a sealingengagement with the axially extending portion 104 of the L-shaped sleeve90 to prevent undesired by-passing of the filter element 28.

Still another embodiment of the combination anti-drainback and reliefvalve of the present invention is illustrated in FIGS. 5 and 6. Aone-piece combination anti-drainback and relief valve 110 is providedwhich comprises a rigid, cylindrical sleeve 112. The lower end of thesleeve 112 terminates in a tubular extension 114 having an outerdiameter which is less than the outer diameter of the upper portion ofthe sleeve 112. The extension 114 is preferably provided with aplurality of circumferentially spaced, radially inwardly projecting tabs116 which facilitate the orientation of the valve 110 relative to theend plate 16 during assembly of the filter unit.

The outer surface of the extension 114 is provided with an annularflange 118. An annular, resilient lip 120, formed of a suitable materialsuch as nitrile rubber, silicone or the like, may be stretch fittedaround the extension 114, disposed above the flange 118. The lip 120extends downwardly and radially outwardly from the sleeve 112 to engagethe end plate of the filter unit radially outwardly of the inlet ports.The lip 120 thus acts as an anti-drainback valve, forming a seal withthe end plate and preventing flow out of the filter through the inletports when the engine is not operating.

The outer surface of the sleeve 112 is provided with an annular seal122, such as the O-ring shown in FIG. 5. The O-ring 122 sealinglyengages an axially extending surface adjacent the inner surface of thecylindrical filter element, in much the same manner as the annular seal102 of the embodiment of FIG. 4 sealingly engages the axially extendingportion 104 of the L-shaped sleeve 90 of that embodiment. The valve 110operates as a pressure relief in the same manner as the valves of theembodiments described above.

In this embodiment, the sleeve 112 is preferably provided with aplurality of circumferentially spaced, radially inwardly projecting ribs124. The ribs 124 provide a sufficient engaging surface for a springcenter tube, such as the spring 40 shown in the embodiments of FIGS. 1,2 and 4, while allowing a reduction in the amount of material used toform the sleeve 112. The sleeve 112 is provided with at least three (3)radial supports, and is preferably provided with six (6) spaced ribs 124as shown in FIG. 6.

In the embodiment shown in FIG. 7, a combination anti-drainback andrelief valve of the present invention is utilized in a filter unit 130including a conventional perforated metal center tube 132. The valve 92is identical to that shown in FIG. 4, and the same reference numeralsare used to designate the elements thereof.

A generally Z-shaped sleeve 134 is secured to the lower end of thefilter element 28 in place of the L-shaped sleeve 90 of the embodimentshown in FIG. 4. The Z-shaped sleeve 134 includes an axially extendingcentral portion 136, an annular flange 138 extending radially outwardlyfrom the lower end of the sleeve 134, and an annular flange 140extending radially inwardly from the upper end of the sleeve 134.

A spring 142, such as a helical compression spring or a wave spring orthe like, disposed coaxially within the filter element 28 engages theinwardly extending flange 140 and the upper end of the sleeve 94, andnormally urges the sleeve 94 downwardly into sealing engagement with theend plate 16 at a position radially inwardly of the inlet ports 26. Thevalve 92 operates in the same manner as in the embodiments discussedabove, but may thereby be used with the conventional perforated metalcenter tube 132.

In still another embodiment of the invention, illustrated in FIG. 8, aone-piece combination anti-drainback and relief valve 150 is provided.As with the embodiment shown in FIG. 4, an L-shaped sleeve 90 is securedto the end of the filter element 28 by any suitable means, such as by anadhesive.

The valve 150 comprises a rigid, cylindrical sleeve 152 mounted withinthe filter element 28 and L-shaped sleeve 90, and adapted for slidingaxial movement relative thereto. The lower end of the sleeve 150terminates in a pair of radially spaced, tubular extensions 154 and 156.The lower end of the outer extension 154 carries a resilient lip 158extending downwardly and radially outwardly therefrom to engage the endplate 16 radially outwardly of the inlet ports 26.

The outer surface of the sleeve 150 is provided with an annular seal 160which sealingly engages the axially extending portion 104 of the sleeve90. The axially extending portion 104 is of sufficient length, and theseal 160 is so positioned, that a sealing engagement is maintainedtherebetween throughout the range of axial sliding movement of thesleeve 150. The seal 160 may be comprised of any suitable material, suchas nitrile rubber, silicone or the like, and may also be of any suitableconstruction, such as an O-ring, a series of O-rings, or the multiplelip wiper type seal illustrated in FIG. 8.

Normally, the spring 40 urges the sleeve 152 downwardly so that the endof the inner extension 156 sealingly engages the end plate 16 at aposition radially inwardly of the inlet ports 26. Additionally, theinner extension 156 is provided with a plurality of radially oriented,circumferentially spaced relief ports 162. Oil is normally blocked fromflowing through the relief ports 162 by an annular, resilient internallip seal 164 secured to the inner surface of the sleeve 152. Should thefilter element 28 become sufficiently clogged so as to cause a build upof pressure above a predetermined amount, the internal lip seal 164 willbe deformed radially inwardly, allowing the flow of oil through therelief ports 162 and exiting through the outlet port 24, therebyallowing the oil to by-pass the clogged filter element 28.

Thus, in this embodiment, the valve 150 is capable of acting as a reliefvalve without requiring axial movement of the sleeve 152. The sleeve 152is, however, still adapted to slide axially within the filter element 28and L-shaped sleeve 90 if and when the pressure builds to the point thatthe force of the spring 40 is overcome, since the pressure required toovercome the flexible internal seal 164 is less than that required toovercome the force of the spring 40. Accordingly, should the pressureincrease to unacceptable levels despite the by-passing of oil throughthe relief ports 162, the sleeve 152 will be moved upwardly so that theinner extension 156 is disengaged from the end plate 16. This allows theoil to flow around the edge of the inner extension 156 and exit throughthe outlet port 24, permitting additional oil to by-pass the cloggedfilter element 28.

The combination valve 150 may be formed as a one-piece unit bypermanently mounting the lip seal 158, the seal 160, and the internallip seal 164 to the sleeve 152 With an adhesive or other suitable meansof attachment. Preferably, the entire valve 150 is molded to form aone-piece unit.

In some applications, where the desired pressure at which the reliefvalve is activated is relatively high, an additional reinforcing spring166 may be required. The reinforcing spring 166 is disposed within anannular groove 168 formed on the radially inwardly facing surface of theinternal seal 164, opposite the relief ports 162. The spring 166 exertsa force radially outwardly to urge the internal lip seal 164 against theinner extension 156. A greater pressure is thus required to overcome thereinforcing spring 166, as well as the internal lip seal 164 itself,before oil will be permitted to flow through the relief ports 162 andby-pass the filter element 28.

In accordance with the provisions of the patent statutes, the presentinvention has been described in what is considered to represent itspreferred embodiment. However, it should be noted that the invention canbe practiced otherwise than as specifically illustrated and describedwithout departing from its spirit or scope.

What is claimed is:
 1. A fluid filter comprising:a. an outer containerhaving a central axis, a closed end and an open end; b. an end platesecured within the open end of said container, said end plate having acentral fluid outlet port and plural fluid inlet ports disposed aroundthe outlet port; c. a hollow, cylindrical filter element enclosed withinsaid container and said end plate; d. a one-piece, combinationanti-drainback and relief valve including:i. a cylindrical sleevemovable along the central axis of said container with respect to saidend plate, one end thereof being disposed within said filter element,and the other end thereof terminating in a pair of radially spaced,inner and outer tubular extensions, the distal end of said outerextension being spaced from said end plate and the distal end of saidinner extension normally engaging said end plate at a position radiallyinwardly of said inlet ports, said inner extension including a pluralityof radially oriented, circumferentially spaced relief ports incommunication with said fluid outlet port, wherein said relief ports arenormally blocked by an annular, resilient internal lip seal secured tothe inner surface of said sleeve, so that when the pressure at saidinlet ports exceeds a predetermined amount, said internal lip seal willbe deformed radially inwardly, allowing the flow of fluid through saidrelief ports and exiting through said outlet port; and ii. a resilientannular lip extending from the outer extension of said sleeve tonormally engage the end plate radially outwardly of said inlet ports;and e. biasing means disposed within said filter element for normallyurging the cylindrical sleeve of said valve into engagement with saidend plate.
 2. A fluid filter as defined in claim 1, wherein said biasingmeans comprises a helical compression spring disposed within said filterelement and having one end thereof positioned adjacent said sleeve.
 3. Afluid filter as defined in claim 2, wherein the diameter of one of theend portions of said spring is smaller than the diameter of the centralportion thereof.
 4. A fluid filter as defined in claim 3, wherein theend of said spring adjacent said sleeve is substantially flat to enhancethe engagement between said end of said spring and said sleeve.
 5. Afluid filter as defined in claim 3, wherein the diameter of both endportions of said spring are smaller than the diameter of the centralportion thereof.
 6. A fluid filter as defined in claim 1, wherein thesleeve of said valve is formed of a moldable polymeric material.
 7. Afluid filter as defined in claim 6, wherein said sleeve is formed ofnylon.
 8. A fluid filter as defined in claim 1, wherein a cylindricalsealing element is secured to said filter element, and an elastomericannular seal is secured to said sleeve, said elastomeric annular sealsealingly engaging said cylindrical sealing element throughout the rangeof axial movement of said sleeve.
 9. A fluid filter as defined in claim8, wherein said elastomeric, annular seal is comprised of a multiplelip, wiper type seal.
 10. A fluid filter as defined in claim 1, whereinsaid sleeve and said lip seal are integrally molded to form a one-piecevalve.
 11. A fluid filter as defined in claim 1, wherein said valvefurther comprises a reinforcing spring disposed within an annular grooveformed on the radially inwardly facing surface of said internal lip sealand opposite said relief ports, said reinforcing spring exerting a forceradially outwardly to urge said internal lip seal against the innerextension of said sleeve.